The present invention relates to a device for distributing materials in bulk with a rotary chute having a variable angle of inclination.
Such devices are used, for example, in devices for charging shaft furnaces, particularly blast furnaces, in which the rotary chute with a variable angle of inclination provides for the distribution of the charge inside the shaft furnace. More particularly, they comprise a supporting structure in which a suspension rotor is mounted in such a way that it can be driven in rotation about a substantially vertical rotation axis. The chute is suspended from this rotor so that it can be pivoted by a pivoting mechanism about its suspension axis. This pivoting mechanism makes it possible to change the inclination of the chute during its rotation. The rotor is traversed axially by a feed channel so that the materials in bulk, which flow from a batch hopper in the charging device, are poured into the rotary chute, which distributes them inside the shaft furnace.
Such devices for distributing materials in bulk are, for example, described in the documents WO 95/21272, U.S. Pat. Nos. 5,022,806, 4,941,792, 4,368,813, 3,814,403 and 3,766,868. In these devices, the pivoting mechanism comprises a second rotor, which has a rotation axis substantially coaxial with the first rotor, from which the chute is suspended. While the first rotor mainly gives the chute a rotation about a vertical axis, the second rotor interacts with the chute so as to determine its angle of inclination. For this purpose, the second rotor is connected to the chute by a mechanism converting a variation in angular displacement between the two rotors into a variation in the angle of inclination of the chute in its vertical pivoting plane. These devices were designed for large diameter blast furnaces. Their pivoting mechanism is too complicated and too expensive to equip small or medium-sized shaft furnaces.
An improved device for distribution material in bulk with a rotary chute having a variable angle of inclination, in which simpler means are used to change the inclination of the rotary chute and which ensure reliable operation, is needed.
A device of the present invention provides a suspension rotor mounted in a supporting structure so that it can rotate about a substantially vertical rotation axis. The chute is suspended from this suspension rotor so that it can pivot about a substantially horizontal suspension axis. The suspension rotor is traversed axially by a feed channel for the chute. It should be appreciated that the present invention proposes a very simple and very compact pivoting mechanism for changing the inclination of the chute in this way. This pivoting mechanism comprises a hydraulic motor, for example a hydraulic cylinder, which is mounted on the suspension rotor and connected to the chute so as to make it pivot about its suspension axis. An annular hydraulic connecting device is used to connect this hydraulic motor to a hydraulic control circuit. This hydraulic connecting device comprises more particularly a non-rotatable sleeve and a rotary sleeve driven in rotation by the rotor. The feed channel for the chute passes axially through these two sleeves, which cooperate in order to connect the hydraulic motor driven in rotation by the rotor to a non-rotatable hydraulic control circuit.
The annular hydraulic connecting device is preferably positioned above the supporting structure, which is designed as a leak-proof housing traversed in a gastight manner or almost in a gastight manner by the upper end of the rotor. This arrangement makes for easier maintenance and shields the connecting device from unfavourable environments (heat, corrosive smoke, vapours, dust) which may prevail inside the supporting structure.
In a first embodiment of the annular hydraulic connecting device, the rotary sleeve is supported by the rotor, and the non-rotatable sleeve is supported by the rotary sleeve. Bearings, comprising for example two bearing rings, may in this case support the non-rotatable sleeve on the rotary sleeve. A flexible annular expansion joint enables the non-rotatable sleeve to be connected in a gastight manner to the supporting structure, while allowing the non-rotatable sleeve small movements with respect to the supporting structure. It should be particularly appreciated that such an annular hydraulic connecting device is relatively insensitive to impacts experienced by the rotor.
In a second embodiment of the hydraulic connecting device, the non-rotatable sleeve is supported flexibly by said supporting structure and the rotary sleeve is supported by the nony, rotatable sleeve. In this embodiment, the non-rotatable sleeve and the rotary sleeve preferably have a fit designed in such a way that a pressurized hydraulic fluid injected between the two warrants a self-centering of the rotary sleeve in the non-rotatable sleeve. It should be appreciated that such a hydraulic connecting device requires fewer sealing joints between the two sleeves, which reduces the cost of the device and the maintenance expenses (fewer sealing joints to be replaced). The elimination of sealing joints between the two sleeves further means a considerable reduction in losses due to friction in the device, given that the power absorbed in a sealing joint may be as much as several kW.
For the transfer of the hydraulic liquid between the non-rotatable sleeve and the rotary sleeve, the hydraulic connecting device incorporates, for example, superposed supply channels. In a preferred embodiment, the drainage means are placed above and below these supply channels so as to collect the leakage flow from the adjacent supply channel. This leakage flow can then be used to supply at least one cooling circuit which is locked to the suspension rotor and rotates with it. In this case, the rotary sleeve advantageously includes a hydraulic circuit communicating with the drainage means and supplying at least one cooling circuit.
A tubular screen, non-rotatable and provided with a cooling circuit, is advantageously inserted between the feed channel and the rotary annular connecting device. This tubular screen is preferably supported by an outer wall of the supporting structure, so as to form with this outer wall an annular chamber in which the annular connection is housed.
In a preferred embodiment, the supporting structure is provided at its lower end with a fixed annular screen fitted with a cooling circuit and defining a circular central opening. The suspension rotor is then provided with a flange at its lower end. Said flange is fitted with clearance in the central opening of the fixed annular screen and has cavities opening into its lateral edge. A gas injection pipe is positioned along the free edge of the fixed annular screen so that a coolant gas can be injected into the cavities of the flange of the suspension rotor. It should be appreciated that such a system of fixed and mobile screens may be advantageously used in any device for distributing materials in bulk with a rotary chute having a variable angle of inclination in order to provide effective separation between the inside of the supporting structure and an unfavourable environment (for example: heat, corrosive smoke, vapours, dust) which may prevail under the supporting structure.
It should further be appreciated that the invention further provides a device for indicating the inclination of the chute. This device may be advantageously used in any device for distributing materials in bulk with a rotary chute having a variable angle of inclination.